dnf提到被排除的包，而它们没有被标记为排除包。

Question

我刚安装了centos8。我试着安装最新版本的docker-ce：

dnf config-manager --add-repo=https://download.docker.com/linux/centos/docker-ce.repo
dnf install docker-ce

然后dnf告诉我：

Last metadata expiration check: 0:19:10 ago on Fri 11 Oct 2019 09:29:33 AM 
CEST.
Error: 
 Problem: package docker-ce-3:19.03.3-3.el7.x86_64 requires containerd.io >= 1.2.2-3, but none of the providers can be installed
  - cannot install the best update candidate for package docker-ce-3:18.09.1-3.el7.x86_64
  - package containerd.io-1.2.2-3.3.el7.x86_64 is excluded
  - package containerd.io-1.2.2-3.el7.x86_64 is excluded
  - package containerd.io-1.2.4-3.1.el7.x86_64 is excluded
  - package containerd.io-1.2.5-3.1.el7.x86_64 is excluded
  - package containerd.io-1.2.6-3.3.el7.x86_64 is excluded

但我没有具体说明任何排除。无论是在dnf.conf中，这里都是我的整个dnf.conf：

[main]
gpgcheck=1
installonly_limit=3
clean_requirements_on_remove=True
best=True

我尝试搜索可用的containerd.io包；但是这些“排除的”包没有出现：

> dnf --showduplicates search containerd.io
Last metadata expiration check: 0:20:30 ago on Fri 11 Oct 2019 09:29:33 AM CEST.
======================================================================================= Name Exactly Matched: containerd.io =======================================================================================
containerd.io-1.2.0-3.el7.x86_64 : An industry-standard container runtime
containerd.io-1.2.0-1.2.beta.2.el7.x86_64 : An industry-standard container runtime
containerd.io-1.2.0-2.0.rc.0.1.el7.x86_64 : An industry-standard container runtime
containerd.io-1.2.0-2.2.rc.2.1.el7.x86_64 : An industry-standard container runtime
containerd.io-1.2.0-3.el7.x86_64 : An industry-standard container runtime

我不太明白为什么dnf会找到这些包裹，但同时又排除了它们.

Answer 1

显然，libsolv中存在一个bug，它导致了您正在经历的“排除”问题(请参阅这里和这里)。DNF使用libsolv，它是一个外部依赖解析器。

您可以使用以下命令安装docker-ce：

dnf --disablerepo=AppStream install docker-ce